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PROJECTS:LED LIGHT BRICK makezine.com/18/lightbrick
LED LIGHT BRICKBy Alden Hart
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PhotographybyGarryMcLeod
Alden Hart is CTO of Ten Mile Square Technologies, a technology consulting firm that develops systems
for media and communications, from the metadata to the metal. In his spare time he combines micro-
controllers, LEDs, mechanics, and other small parts in ways that have no practical application.
Set up: p.105 Make it: p.106 Use it: p.111
A LITTLE GLOWING FRIENDRestful, multicolored lights illuminate
your path to the kitchen for a late-nightsnack. Rediscover the night light as anenergy-efficient way to brighten yourhome.The Little Glowing Friend (I named it after the ever-vigilant
blue canary night light in a They Might Be Giants song) uses
a single-chip microcontroller to drive 20 LEDs in a variety ofpatterns. The circuit is embedded in a clear resin casting,
creating a lively, self-contained display. The light brick takes
about 2 watts of power, and should last more than 10 years
in continuous operation.
I gave away 24 of these in 2006; most have been on ever
since, and there have been no reported failures. Electricity
cost is about $1 a year, for 247 operation.
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makezine.com/18/lightbrickPROJECTS:LED LIGHT BRICK
Illustrationb
yNikSchulz
CHIP AHOYThe heart of the Little Glowing Friend is a single-chip
microcontroller (PIC16F916) thats programmed
using PIC assembly code.
This chip provides the following functions:
Drives the LEDs directly from the chips output pins
Provides 20 dimming channels one for each LED
Stores and runs the light patterns
The printed circuit board (PCB) holds the PIC
microcontroller, LEDs, current-limiting resistors,
a DC power connector, and a few other parts.
The PIC chip is capable of driving up to 25
milliamps (mA) of current per output pin to the LEDs.
A current-limiting resistor is used to limit the current
flowing through each LED to about 20mA. There
are 2 decoupling capacitors that clean up any noise
that might be on the power supply. Finally, oneresistor is used to hold up the PICs reset line so the
chip can run, and another is used for the switch.
Because LEDs glow at only one intensity,
dimming is accomplished through a
variant of pulse width modulation (PWM)
flashing the LED on and off so fast that your eye
sees it as a brightness level less than 100%.
Once the circuit is working, the entire board is
embedded in a clear resin casting that lights up in colorful
and interesting ways. You can make your own mold as part
of the embedding process, so the brick can take on anyshape and texture you desire.
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PhotographybyAldenHart
SET UP.
MATERIALS
[A] Circuit board from the
light brick kit or make your
own from the CAD files. Both
are available at makezine.
com/18/lightbrick.
[B] PIC16F916 micro-
controller labeled as U1 on
the PCB and the schematic,
which is also available at the
link above
[C] LEDs, 5mm, 20mA,
wide viewing angle, 0.100"
lead spacing (20) 5 each,
red, yellow, green, and blue,
D1D20 on the PCB and
schematic
[D] 100resistors, watt,
5% carbon film (20)
R1R20
[E] 20kresistors, watt,
5% carbon film (2)
R21, R22
[F] 10F capacitor,
tantalum, 16 volts,
0.1" lead spacing C1
[G] 0.1F capacitor,
monolithic, 0.100" lead
spacing C2
[H] Rolling ball tilt switch,
0.100" lead spacing SW1
[I] DC power connector,2.1mm ID coaxial J1
[J] Rubber bumpers
or feet (4)
[K] DC power supply (wall
wart), 5V DC regulated,
300mA or more, 2.1mm
ID/5.5mm OD, center
positive I recommend a
400mA supply because
sometimes 300mA ratings
are a bit optimistic.
[L] 12" length of #14 solid
wire (optional)
[M] 22pF capacitors,
monolithic or ceramic
disc, 0.100" lead spacing
(2, optional) C3, C4
[N] Single-row header
connector, 6-pin, 0.100"
(ICSP connector)
For molding, use O and P to
make your own mold, or use
Q instead.
[O] Silicone RTV Mold-
Making System, 1lb silicone
and 0.1lb catalyst from TAP
Plastics (tapplastics.com).
My mold used all 16oz; if
you design a bigger mold,
get more.
[P] Lego bricks for building
a mold box
[Q] Self-releasing polypro-
pylene mold, 3"5"15"
such as Castin Craft MC-7,
part #43893
[R] Clear-Lite polyester
casting resin, 16oz
from TAP Plastics
[S] MEKP liquid catalyst,
oz
[T] Paper cups, 12oz or
16oz (2) for measuring
and pouring
[U] Stirring sticks (2)
[V] Clear gloss resin spray
(optional) such as Castin
Craft Resin Spray, for cover-
ing imperfections
NOTE: A complete bill of
materials and tools, with
sources, as well as mold-
making and resin-casting
instructions, are available
atmakezine.com/18/
lightbrick.
A
E
F
Q R
T
S
U
V
H
I
D
J
B
C
K
G
M
O
P
NL
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PROJECTS:LED LIGHT BRICK makezine.com/18/lightbrick
BUILDYOUR LEDLIGHT BRICK
START>>
MAKE IT.
Time: A Weekend Complexity:Easy to Difficult
1. ASSEMBLE THE CIRCUIT BOARDFirst, locate the top and bottom of the PCB. The top has the
silk-screen and component designators. The bottom has mostof the wiring.
1a. Solder the resistors first. Use 100resistors for R1R20,
and 20K resistors for R21 and R22. Resistors are not polarized,
so its not necessary to line up the color codes, but it does
make for a neater job. Tape the resistors tightly to the top of
the board using blue masking tape; theyll trap air bubbles
underneath them if theyre not down tight.
Flip the board over and solder. If any of the resistors shifted,
heat them up and push them back down. Cut the leads downto the solder joints with wire cutters and remove the blue tape.
Building the light brick involves 3 steps: assemble the PCB, build (or buy) the mold, and cast the piece.
The project can be done over a weekend, with each step taking a few hours. Some steps require a wait
time, so the total build requires at least 2 days and an overnight to cure the casting. The project is
designed at multiple levels of difficulty:
Easy:Assemble the circuit board from a kit and do the acrylic embedding with a pre-made mold.
Medium:Assemble the circuit board from a kit. Then do the mold construction and casting.
Difficult:Program the PIC yourself, to make new patterns. If you want to get really advanced, you can lay
out and make your own circuit board allowing you to change the size and layout and even the number
of LEDs. You could also free-space the wiring. All the source materials to do this are available online.
For kits, CAD files, firmware, and additional documentation, visit makezine.com/18/lightbrick, or my
website attenmilesquare.com/light-brick.
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1b. Place capacitors C1 and C2 on the board. The tantalum
capacitor C1 is polarized and must be inserted as indicated on
the board. The positive (+) side of the capacitor goes in the +
hole, which is the square one. Tape, solder, and cut as before.
1c. Carefully bend the leads of the PIC to fit the boards chip hole
spacing. Place the PIC with pin 1 (the indented end) pointing to
R21 and R22. Carefully solder, without putting too much heat on
any pin. Double-check that the polarity is correct before soldering.
1d. Attach the DC power connector J1. Bend the blades out
somewhat from the bottom to hold the connector in place.
Then solder it in flush to the surface of the board, using plenty
of solder to seal the holes.
1e. Attach LEDs D1D20. The patterns are programmed for the
following layout of LEDs:
R B G Y R
Y R B G Y
G Y R B G
B G Y R B
Be sure to test your LEDs for function, and for color if its not
obvious by the casings. Use an LED tester or just squeeze the
leads onto a 3V lithium coin cell.
For proper casting, you want the tops of all the LEDs to be
roughly level, and taller than the power connector. The holes in
the PCB are sized so that a standard LED lead will stop about
1" above the board. Its a tight fit, but it works.
If for some reason your LEDs dont have this stop, youll need tomake spacers. Make 20 spacers by stripping2" of insulation
from #14 solid wire. Insert the insulation between each LEDs
leads, up by the LED case.
Place the LEDs in the board and test the heights against the
power connector. Observe correct polarity when placing the
LEDs. The long lead is the positive, or anode (A), and goes
through the round hole. The short lead is the negative lead, or
cathode (K), and goes through the square hole (mnemonic:
cats are negative). If theres a flat spot on the LED it will be
on the cathode side.
NOTE: The square hole here is designated differently from the
capacitors, which is the opposite.
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PROJECTS:LED LIGHT BRICK makezine.com/18/lightbrick
1f. Turn the board upside down on a hard, flat surface to ensure
all LEDs are lined up. Solder, and clip the leads. Remove any
spacers using hemostats or fine pliers. Notice that the common
rail is connecting all the positive (+) pins of the LEDs. (In some
other LED projects there is a common ground () for all the
LEDs.)
1g. Attach tilt switch SW1. The tilt switch is a rolling ball that runs
on a track and closes (activates) when the ball rolls to the base
where the wires stick out. It provides user input, acting like a but-
ton push or mouse click. The tilt switch is the only component
that goes on the bottom of the board. It doesnt have a polarity.
If you want it to activate when you tip the brick back toward the
power connector, the switch must angle downward from the rear
of the board, as pictured.
If you want this orientation, mount the switch on the bottom of
the board through the switch holes labeled SW1. Leave about "
of the switch leads exposed between the switch and the board.
Youll need enough room to bend the leads to angle the switch.
Use the SW2 position if youd rather the switch activate 90 from
the SW1 position.
1h. If you intend to program the PIC in-circuit, youll need to attach capacitors C3 and C4 and the
programming header J2 at this point.
1i. Dont plug the board in just yet. Visually inspect the PIC and
the rest of the board for solder bridges (i.e., short circuits in your
soldering). Remove any bridges with solder wick (for advice on
how to do this, see makezine.com/18/lightbrick).
Next, test the board for a short circuit. Use a continuity tester
or ohmmeter to test the power connectors + and terminals
(located on the bottom of the board).
Finally, test that you have a good power supply. The center pin
on the power supply connector should be a stable +5V, and the
sleeve is ground. Be sure not to short out these contacts during
this test! The board will actually work between about 4V6V.
The PIC doesnt like voltages above 6V and may blow out if over-
voltage is applied.
If the board passes these tests, then plug it in! If the board
doesnt work properly, consult the Troubleshooting section on
page 111. Dont cast the brick until the circuit is working reliably.
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2.MAKE THE MOLD
AND CAST THE BRICK
Since weve covered moldmaking and casting in a previous issue
(see MAKE, Volume 08, page 160), we wont detail the process
here. Complete moldmaking and resin casting instructions
for this project are available at makezine.com/18/lightbrick.
The easiest way to get a mold is to buy a pre-made one like the
MC-7 (see Materials list). Its 3"5"15", a reasonable fit.
I prefer my own mold, for a better fit and a more interesting
finished piece. The circuit board is designed to fit nicely into
a volume 3"4"1"2" deep, but you can make the master
mold any size and shape that will accommodate your board.
Remember that the power connector needs to be flush against
one side of the finished casting.
You can also house the Little Glowing Friend circuit board in any container you desire, but I l ike the
permanence and uniqueness of the cast brick.
3. FINISHING UP3a. Dont get impatient and demold the piece too early, as this can ruin it. Follow the manufacturers
recommended demold times, and then some. Its best to leave it overnight or even longer.
Remove the brick when its truly cured. It should be fully cooled and hard. Resin hardens from the inside
out, so the surface is the last part to harden. This can take well over a day depending on the mix and
conditions. Dont judge by time; demold only when the surface is hard and no longer tacky. Test hardness
using a stick, not your finger.
You can speed the surface cure by warming the brick under some lights, but be careful not to overheat
the casting or the mold. Dont leave the lights on overnight or unattended.
3b. Remove the tape from the power connector using hemostats. You may also need a knife if its gotten
coated over.
3c. Even though the brick is hard at this point, the finish is still fragile. It will pick up fingerprints and
will pit with dust. Its best to handle it only by the edges. You may want to tent it under wax paper and
continue the cure. Dont let the wax paper touch the surface, or it will leave marks. Optionally, you can
spray on a surface coat of resin at this point to protect the finish, but be aware that this may cloud the
surface. Use sparingly.
3d. Apply the bumper feet to the bottom and youre done.
FINISH X NOW GO USE IT
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PROJECTS:LED LIGHT BRICK makezine.com/18/lightbrick
MEET PEGGY, OUR COVER SPOKESLIGHTBy Gareth Branwyn
Geek super-couple Windell Oskay and Lenore
Edman like to trip the light (emitting diode)
fantastic. One of their first projects to blip theglobal DIY radar was their interactive LED dining
table, with 448 LEDs under frosted glass.
After the bizarre Mooninite Invasion of 2007,
when some Lite-Brite-type signs got the betterof Bostons finest, Oskay and Edman, who invent
under the name Evil Mad Scientist Laboratories
(evilmadscientist.com), were inspired to create
Peggy, a plug-and-play (or plug-and-program)LED pegboard you build from a kit.
With the success of Peggy, the white coats at
EMS Labs knew they were on to something. Itbecame clear that there was room for something
more advanced, says Oskay. So we made the
Peggy 2, which has the same basic design butsupports simple animations.
Recognizing the strength of the Arduino
community, they designed Peggy 2 to be pro-grammed through the Arduino environment.
The architecture is similar to that of an Arduino
clone, but with substantial onboard LED driving
hardware, he says.
So how long does it take to build a board with
up to 625 LEDs? An hour or two on the rest ofthe board, and then the time to solder on the
lights. You decide how many you want to install
the resolution of your screen. Only rudi-mentary soldering skills are required. To create
a basic sign lighting every LED, no programming
is needed. To animate Peggy, and create other
lighting effects and control, programming canbe done via Arduino.
People love interacting with the Peggy, saysOskay. Theres something about giant pixels especially giant physical pixels that you can
touch that really grabs people. We love seeing
what folks do with it. One builder, Jay Clegg,even figured out how to display grayscale video
on the Peggy 2.
The original Peggy is $80 and Peggy 2 is $95,
LEDs not included. Both kits are available in theMaker Shed (makershed.com) and the Evil Mad
Science Shop (evilmadscience.com).
Gareth Branwyn is senior editor at MAKE.
Photograph
byGarryMcLeod
GarduinoGardenControllerpage 90 >>
DIYENERGY Build a SustainableFuture at Home page 45GETOFFTHE GRIDSolarWater Heater
No-WattLaundry
GEEK YOURGARDENMicro Irrigation
IndoorComposting
REBOOTYOUR HOME CutYourPower Bill
TwitterYour Kilowatts
32
PLUS:Make YourOwn
Programmable
LEDDisplay
page110
PROJECTSto Make aDifference
makezine.com
M_C1 C4_UPC SBN_F1 indd 1 4 15 09 4 51 47 PM
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111Make:
FIRE UPYOUR LITTLEGLOWING FRIEND
USE IT.
Plug it in and watch it go! Activating the tilt switch
will cycle the device between power off and 4
different lighting programs Waves, Colors, Calm,
and Frenetic.
TROUBLESHOOTING
If, for some reason, the board doesnt light when
you test it (in Step 1i, before casting the brick,
of course), check the following:
Ensure that all leads go through the holes, and
check that none of the PIC leads have folded up
under the chip body. They should all be visible
from the bottom of the board.
Inspect the bottom of the board to ensure that
all connections are soldered.
Check the polarization and orientation of compo-
nents C1, U1, and D1D20.
Check that there are no solder bridges (two
points connected that shouldnt be).
Check that the power supply is plugged in and
outputting between 4 and 6 volts. Use a volt/ohm
meter (VOM) or multimeter.
Check that the center pin of the power supply
is positive, not negative (reversed polarity).
Check that the board is not short-circuited bytesting the + and terminals on the bottom
of the board.
If some LEDs are working but not others, try doing
the following:
Test the LED individually. Apply voltage from
a coin cell across the LED terminals.
Next, test with a VOM that there is 100 ohms of
resistance between the LEDs negative terminal
(the square hole) and the PIC pin. Trace thecircuit visually or use the schematic diagram.
RESOURCES
For a materials and tools list, sources, CAD files,a schematic, and moldmaking and resin-casting
instructions, visit makezine.com/18/lightbrick.
Connecting LEDs: makezine.com/go/led2
Free-space wiring example: instructables.com/
id/3x3x3-LED-Cube
Video on how to remove solder bridges with
solder wick (see 7:45): makezine.com/go/solder
Thanks to Daniel Klaussen for helping us in testingthis project.
PhotographybyAldenHart
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